The parlamentary committee of enquiry did invite Snowden in 2013, but the government blocked it - they weaseled around it, based on “cannot guarantee Snowden’s security” and “the US would be mad at us”.

The committee on the NSA affair sued the government, and the Bundesgerichtshof (highest ordinary court in Germany) decided that the government has to invite Snowden as a witness and ensure his security - the rights of the parliament are more important than the national interests as seen by the executive.

The Federal Court of Justice (BGH) has ruled that the government must bring US whistleblower Edward Snowden to Berlin to answer parliamentary questions on the NSA, according to the Süddeutsche Zeitung.

as better reporting comes in: this is not exactly the content of the court ruling. the government is forced to give a real and binding answer if the committee asks again to invite Snowden as a witness.